If the roofing was already attempted to be stuck down as you say, more than likely no way of salvaging it. The glue did not stick the first time which would tell me that any glue applied again will not stick and I do not believe there is anyway to remove the glue from the roofing. What type of material did he use? What brand rubber? What brand glue? Maybe a link to the instructions as well.

As of today, I don't know the brands, because he was so upset at the time it was happening, that I didn't have the heart to ask nitty gritty details. Rather i was preoccupied trying to cheer him up, due to his having gone way beyond the 9-yards in preparation (long story). I did ask prior to application if the rubber is a thick gauge, and he said that yes, it's a thicker gauge than the 3-foot standard, but also less flexible to maneuver.

I believe they needed to hammer nails into the overlap (overlapping onto the side wall & front, otherwise it failed to "flop" over & stick, rather it stuck out beyond perimeter of patio, if not for the nails.

The glue was yellow & extremely toxic smelling. Both him & his 2 quite-experienced men had mixed it per instructions via heated mixer. I sometimes still smell it inside the adjacent kitchen, despite having the attic fan on Sun. & Mon. with windows open facing the non-toxic areas of house. It was raining today, so maybe that helped dilute the toxicity, but I can't be sure yet.

I would have definitely wanted to observe, but because i'm very chem-sensitive, I couldn't get within 20 feet of it without feeling ill. It even "sorta" bothered them, and they were strong men.

Note i'm somewhat uncomfortable w/posting this on a public forum because he's a well-reputed guy with decades experience and referred by yet another top-recommended guy (both licensed & insured). The assistants he had working with him were also supposed to be experienced.

What kills me most, is that this toxic glue is still referred by managers at construction supply places, instead of them exclusively recommending torching instead. It's not that I didn't know about torching, rather the licensed guy who referred him to me strongly advised me that contractors don't like you to tell them how to do their jobs. And that leaves desperate people like myself at the mercy of shop guys who misguide customers (as in this case).

He said that if he'd known what would happen, he wouldn't have agreed to to do the job. He offered to give his insurance info, while expressing [brokenly] that he doesn't like the idea, as this is the first time anything like this happened to him. As for my part, I myself (while tempted) am loathe to contact his insurance company, since he's been much nicer and reliable than most others around here, and i really need him for some other major jobs. And after all, with this junky rattletrap of an old house, does it pay?

Basically it amounts to a toss-up between:

(1) risk of ill-feelings (even if unexpressed), for what? For this:
(2) headache dealing with insurance company for an old rattletrap house that has zillions of stuff wrong with it (which he knows about, including mold issues, old pipes, crazy landscaping issues, constant bee infestation, you name it.

I understand, the glue down or mop method of attaching the rubber is quite common today as opposed to the torch down. I was asking mainly as I was trying to see if that may lead me to any type of clue of what may have been wrong. It sounds to me as if he did things correctly as you mentioned so from here I have no clue what may have happened.

Today I noted that on the rubber there's some text.
I couldn't make out all of it (some was too blurry), but it's something like this:
????RAAB
GOOEPWMER
Made in USA

Note that in past years, the patio had been subjected to various treatments, such as silicone & also was painted, but that was so long ago, that it was practically like raw concrete by now.

And yes, I know that glue is recommended, but the ones who do so should make standard practice the following:

(1) Warn re: which weather conditions to avoid
(2) be prudent & strongly advise customers to provide an emailed pic. of the area it's being applied to, so they can better suggest which method is best for that particular situation.

I've had something sorta similar happen to me before, believe it or not (yes, lightening can strike 2x in variable ways).
A few years ago, I asked a boy who worked at a tool rental place if he knows anyone who can both sand one of my bedrooms & apply polyurethane. He said he can, so I hired him. The idiot failed to follow the instructions on the polyurethane container which stated that that it requires thorough stirring. Instead he shook the can a couple times & proceeded.
Result:
Extremely toxic smelling house, since the stickiness never dried. It was a nightmare requiring resanding, and then redoing polyurethane (the 2nd time around I used a water-based polyurethane by same company).

It's been raining alot today & yesterday, and water has been collecting within the rubber creases. I just hope this won't impact on the water-proofness??
...since the only reason I had the job done was so I can finally have a dry garage, rather than its roof being like a sieve.